We're going to go straight to our Tom Foreman, who has keen insight into Louisiana voters. He's been tracking the exit poll data all evening.

Tom, how can we make this call at closing -- at closing time for the polls?

TOM FOREMAN, CNN CORRESPONDENT: Well, you said the exit poll data, Don. Really that's it. This is a case where all you have to do is the math because it is overwhelming. Look at this. The number one issue to all of the voters today was the economy. And not by a little bit. A massive amount. This is just one of the indicators here.

Look at who voted today. The biggest single group in this was people who made $50,000 to $100,000 a year. But if you look at everybody from $200,000 on down in income, down here we have $200,000 or more, look at who won in these categories. Rick Santorum, at least in terms of what we heard from the exit polls, everybody in each of these categories said they wanted him and they're the ones that they voted for. And look at how massively, particularly we look at the numbers down here.

In this case Santorum, 48 percent. Gingrich got the second number. Romney comes in here at 22 percent, tied with Gingrich. But still a massive lead for Santorum. Even bigger when you go down here to the under 30,000. Look at that. Santorum, 64 percent. Romney tied with Ron Paul at 12 percent.

The only area in which Mitt Romney won was in people who made $200,000 or more. And look at this. Even in that area he has a substantial lead, but only 45 percent to 31 percent. That's simply not enough to overcome what Santorum did in all the other categories, especially if you look at the state over here in terms of median income. I'm going to pull this out. The darker parishes here are the ones where people make more money.

And here's the problem. Even if Mitt Romney's winning there, look at the size of these. Here's Assumption Parish. Less than half a percent involved in that parish. Go up here to Tangipahoa Parish. Tangipahoa Parish, this is the biggest one, 2.3 percent of the population. Right next to it Saint Helena Parish, less than .2 of 1 percent. And you can all the way up here, you can find another big one. Monroe, less than .3 of 1 percent.

This is the reason that we're able to make this projection, Don, because not just this factor but many others. When you look at the economy alone, though, you can see the numbers simply stack up very badly in one of the states with the lowest income in the country, you simply can't win by winning the people who make over $200,000. So we'll watch the numbers come in. But the exit polls say this is a big, big win for Santorum.

LEMON: Tom, you're bringing me back to my youth hearing all the names of those parishes as I grew up in Louisiana.

FOREMAN: My time living there, too. We both had a good time.

(LAUGHTER)

LEMON: Absolutely. Thank you, sir. We'll check back in. Tom Foreman. And more on Rick Santorum's big win in Louisiana and what that means for a divisive battleground stage for the Republican presidential nomination in just a moment.

Our Joe Johns is on the ground there. We'll speak to him.

But first we also are following another breaking story here. Former Vice President Dick Cheney has undergone heart transplant surgery.

Mark Preston standing by in Washington.

Mark, what do we know right now?

MARK PRESTON, CNN SENIOR POLITICAL EDITOR: Well, Don, we've been told that the former vice president is recovering in a suburban Washington, D.C. hospital after undergoing that heart transplant. The former vice president's heart problems have been very well documented and his office says that he has been on the cardiac transplant list for more than 20 months.

Now right now Dick Cheney is in intensive care, and his office tells us that they do not know the identity of the donor, but the family will be forever grateful for this life-saving gift.

Don, Vice President Cheney, 71 years old. We'll have more on this developing story throughout the night.

LEMON: All right. Vice President Cheney gets a heart transplant. Our breaking news. As well as Rick Santorum. CNN projects has won the Louisiana primary.

Next, we're going to go to CNN's Joe Johns, who's standing by on the ground in New Orleans.

Hey, Joe. What do you know? You're talking to voters there. You've been hearing from them. What do they make of this? What are they saying?

JOE JOHNS, CNN SENIOR CORRESPONDENT: Well, we have been talking to voters here in Louisiana. Actually been here on the ground all week, Don. And it's very interesting for a number of reasons. Louisiana is one of those many states that just for decades really has not been involved in the Republican primary process the way they've been involved this year. So it was sort of a novelty for these four candidates to descend on this state at this time and start asking them for their vote. So we would see events with just about two dozen seats set up or whatever and just a row of TV cameras. Very unusual.

One of the things that was pretty par for the court with some of the other primary states, though, was the robocalls, tons and tons of robocalls. We're told most of them that people heard from were actually Santorum. Possibly one of the most interesting ones was a robocall that was put out there by Hank Williams on behalf of Rick Santorum. Hank Williams being the well-known recording artist.

So you look at that. Perhaps that was a little bit of an issue. Another issue I think here was turnout today across the state of Louisiana. There were expectations that turnout would just not be that good. I know at the polling place where we were the turnout certainly wasn't that good. All day long.

Why? Well, for one thing, there wasn't the kind of retail politicking that you've seen in some of the other states because this is all a very new process for people in Louisiana and they just didn't, some said, have the connection with these candidates you that might have seen in New Hampshire. And connection perhaps the key.

Again, in a southern state, Mitt Romney, who is the leader according to the national polls, was not able to connect with the voters here in Louisiana. Rick Santorum certainly was. Reaching across to evangelicals, Catholics, and that may very well have been the difference in Louisiana.

So back to you, Don. We'll come back and talk about it a little bit later.

LEMON: Joe Johns, thank you very much.

CNN following breaking news from Louisiana. CNN projects Rick Santorum has won the Louisiana primary. We're going to get more on his victory coming up next, right after a quick break.

(COMMERCIAL BREAK)

LEMON: Breaking political news. CNN projects that Rick Santorum has won the Louisiana primary, giving the former Pennsylvania senator another win down south.

With our political team of experts here. You all know them. CNN's Tom Foreman and our political director Mark Preston in Washington and senior correspondent Joe Johns standing by in New Orleans.

Tom, I want to get to you. You showed us some metrics by which people went in to vote what was on their minds. You were talking about the economy and really a very wealthy guy just didn't seem to relate to the people of Louisiana in a state that you said is among the poorest, couldn't relate to a wealthy guy. I'm wondering, though, in a state that you said is among the poorest, couldn't relate to a wealthy guy. I'm wondering, though, in a state like Louisiana is there any appeal for Rick Santorum among moderates or liberals?

FOREMAN: Well, that's an interesting question because when you talk about the metrics here that's another one you have to consider. One of the things that Rick Santorum has done very well with is the very conservative voters. They showed up in the biggest numbers today. This is a conservative state in many ways. Look at the win that he had here, 52 percent to 24 percent for Romney. Better than 2-1 among very conservative voters.

That's no big surprise. But if you look at what he had next year, the somewhat conservative voters, again he pulled out a win by 10 percent here. And here's the one that really makes a difference. In the moderate or liberal voters he even edges it out there by 8 percent there.

LEMON: Wow.

FOREMAN: That's pretty substantial. So once again he gets a sweep of all three. However, I wanted to put a caution in here, Don, that you will understand particularly being from Louisiana, as I have been. There's no real litmus test of what makes somebody moderate or liberal or somewhat conservative or very conservative. That can change somewhat state to state.

I would theorize that to a degree the moderates or liberals in Louisiana, particularly the moderates, may be a bit more conservative than they are in many other states. I think they probably are. So does this mean that Rick Santorum has somehow unlocked the Rosetta stone here, that he's figured out how to get into this moderate or liberal base that Mitt Romney has been able to rely on elsewhere?

I'm going to say probably not. I think what it means is that he was in a state where it was really well primed for him to come in as a very conservative candidate and do well and indeed he did, Don.

LEMON: Earlier you spoke about what was on voters' minds. Number one, the economy. And just speaking to my mother and other people who still live there, education also very important because Louisiana ranks at the bottom, too, as well for education.

FOREMAN: Absolutely. Those are big, big, big factors here for an awful lot of people in the state. And there's no question that a lot of people vote that way. Again, you have to think about those in the context of the state. This is something that works well to what --

LEMON: Yes.

FOREMAN: What Rick Santorum has been selling out there. Mitt Romney tends to do better with people who are better educated and overall, if you look at bachelor's degrees and higher degrees, that sort of thing, Louisiana doesn't have as many of those as some other states, so again, friendly territory for Rick Santorum, not so friendly for Mitt Romney. LEMON: All right, Tom Foreman, thank you. Very interesting.

We're following another breaking news story as well. It involves politics. Former vice president Dick Cheney has undergone a heart transplant surgery. Mark Preston standing by.

Mark, give us the very latest.

PRESTON: Well, Don, what we've learned today from the office of Dick Cheney is that in fact he is recovering in a suburban Washington, D.C. hospital after undergoing a heart transplant. The former vice president's heart problems really well have been documented, Don. We've known so much about them over the years. He has been on the cardiac transplant list for more than 20 months.

Well, right now the former vice president is in intensive care. He is recovering. And his office tells us that they do not know the identity of the donor. But of course they are very, very grateful for the donation.

Don, we should say Vice President Cheney is only 71 years old. And of course as we hear more about his condition throughout the night we'll update you on it.

LEMON: All right. Thank you very much, Mark Preston.

Joe Johns, our senior correspondent, standing by in Louisiana to follow up on Rick Santorum's big win down there.

You heard me talking to Tom Foreman. He says education -- that Mitt Romney doesn't do well with the folks down in Louisiana. Obviously, you see he didn't win. Rick Santorum doing very well among conservatives. Among moderates. And even liberal voters as Louisiana sees them.

JOHNS: That's really fascinating. That's just a fascinating development. But Rick Santorum really continues to surprise in a lot of ways. You know, earlier in this race in some other states he was having problems getting Catholic voters to vote for him, and that seemed very unusual. It was sort of defying expectations.

Well, now all of a sudden apparently a connection with some of those more liberal voters. It's almost, you know, inexplicable, I would say, because Rick Santorum talks such tough talk on the campaign trail and in many ways he is more conservative than the other true conservative in the race who would be Newt Gingrich. So considering all of that, it'll be interesting to see how he does going forward.

But the one thing I think we also have to point out, Don, is the delegate count, which is a work in progress this evening.

LEMON: Right.

JOHNS: Nonetheless, I want to just sort of run through for you how this thing is supposed to work because the delegates are what all of this is about. You know? Each of these candidates is racing around the country trying to amass as many delegates as possible to the Republican national convention in hopes of getting that magic number, 1144, to go into the convention as a winner.

Rick Santorum certainly is running in second place. Mitt Romney running in first place. But the way it works here in this state is tonight, 20 delegates are supposed to be assigned to a candidate.

LEMON: Hey --

JOHNS: Yes?

LEMON: And Joe, we've got --

JOHNS: You got a question, Don?

LEMON: Yes, Joe, we've got to run, too. Thank you, sir. Appreciate you but we also have a delegate update now. We're going to go back to Mark Preston.

Mark, this just in. You heard Joe explaining a little bit there. You have more on this. What do you have?

PRESTON: Well, Don, yes, and Joe is right. There were 20 delegates on the table in Louisiana and CNN now projects that Rick Santorum will get at least eight of those delegates. Very complex rules down there, as Joe again was explaining.

We can also project right now that Mitt Romney will come in second place in the Louisiana primary. He too will get some delegates. We're still trying to figure out the math on that right now to see what he will come in at.

Newt Gingrich, Ron Paul will walk away with goose eggs. They will have nothing to show for the Louisiana primary, Don, which raises a whole lot of questions about how much longer Newt Gingrich can really stay in the race. And of course Ron Paul has really made it clear that he has no plans of leaving.

LEMON: Mark, we have about 15 seconds left here. When we're talking about the delegates, if you do the math, is it mathematically -- mathematically possible for anyone else besides Mitt Romney at this point?

PRESTON: It is mathematically impossible. It is probably improbable right now for anyone except Mitt Romney to get 1144 heading into August, into the RNC convention, Don. However, Mitt Romney still has a long road ahead of him to get to 1144.

Make sure you join me tonight 10:00 p.m. Eastern for complete coverage of the Louisiana primary right here in the CNN NEWSROOM. I'm Don Lemon. Piers Morgan right after this.

(COMMERCIAL BREAK) (21:47)

LEMON: Hello, everyone. I'm Don Lemon live at the CNN world headquarters in Atlanta.

We have some breaking news. As we reported at the top of the hour, CNN projects Rick Santorum has won the Louisiana primary, giving the former Pennsylvania senator another win in the south.

Take a look at the numbers now. Forty-six percent for Rick Santorum as we speak. Mitt Romney 28 percent. Newt Gingrich 18 percent. And 6 percent for Ron Paul. Of course, it's only 19 percent of the entire electorate and everyone who's voted.

Hey, listen, I want to bring in our political director now, Mark Preston in Washington.

Give us some analysis of this, Mark.

PRESTON: Well, Don, of course as you see Rick Santorum has got a big win in regards to momentum for this race for the Republican presidential nomination. CNN can also estimate right now that Rick Santorum will get at least eight delegates from this win in Louisiana, Don.

We can also project at this point that Mitt Romney will come in second place. Third place will go to Newt Gingrich. Fourth place will go to Ron Paul. We also do know at this time that Newt Gingrich and Ron Paul will receive no delegates from tonight's contest -- Don.

LEMON: So no delegates. Interesting stuff here. So listen, I want to -- want to go to another break and pivot here to another story. Breaking news that we're following tonight involving the former vice president of the United States, Dick Cheney, Mark.

PRESTON: Yes, Don. A story we've been following for the last couple of hours now. We've learned that Dick Cheney is recovering in a suburban Washington, D.C. hospital after undergoing a heart transplant. The former vice president's heart problems had been very well documented. And his office tells us that he has been on the cardiac transplant list for more than 20 months.

Right now, Don, Dick Cheney is in an intensive care unit and his office does tell us as well that they don't know the identity of the donor.

Don, Dick Cheney is 71 years old. We'll have more on this story next hour.

LEMON: I was going to say, 71 years old, that's not -- I mean, that's fairly young now, especially today's standards of living and that and what have you. Did he have four or five -- he survived four or five heart attacks before?

PRESTON: Yes. He's had -- he's had them since such a young, young age. As you said, 71 very young, but this has been ongoing for the vice president throughout very much of his adult life. But as we've heard right now from his office, he seems to be recovering --

LEMON: Yes.

PRESTON: -- fairly well right now in a Washington hospital.

LEMON: Two breaking political news stories we're following along with my colleague here, Mark Preston. Rick Santorum has won the Louisiana primary and also Dick Cheney recovering from a heart transplant right now.

I'm Don Lemon. I'll see you back here at the top of the hour, when we follow up on both of these developing stories including the latest on the Trayvon Martin case.